Adaptive ANR Circuit Loop Gain Adjustment for Power Efficiency

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Solution Overview

Problem

Existing personal active noise reduction (ANR) devices face issues with high power consumption, limited frequency range, and the generation of unwanted noise, leading to short battery life and unpleasant sound experiences.

Innovation Solution

An ANR circuit that monitors environmental noise levels using an external microphone, adjusting the feedback-based ANR by varying the loop gain and filter coefficients to optimize noise reduction, thereby enhancing power efficiency and sound quality.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If feedback-based ANR is continuously provided at high degree, then noise reduction performance is improved, but power consumption increases leading to short battery life

Engineering Contradiction:

Improvenoise reduction performanceVSAvoidpower consumption

Core Design Contradiction:

ReliabilityVSUse of energy by moving object

Solution Approach 1:

The patent applies dynamics by making the ANR degree adjustable and adaptive rather than fixed. The system dynamically changes the loop gain and filter coefficients based on environmental noise levels detected by an external microphone, allowing optimal performance across varying conditions while reducing power consumption when full ANR is not needed.

Inventive Principle:

Principle #15Dynamics

Solution Approach 2:

The patent changes key parameters (loop gain and filter coefficients) of the ANR system based on environmental conditions. By monitoring noise levels and adjusting these parameters accordingly, the system maintains effective noise reduction when needed while reducing power consumption during quieter periods or when full reduction is unnecessary.

Inventive Principle:

Principle #35Parameter changes

2Reliability

If feedback-based ANR is provided with fixed high loop gain, then noise reduction at certain frequencies is improved, but unwanted ANR-originated sounds and instability increase

Engineering Contradiction:

Improvenoise reduction effectivenessVSAvoidunwanted noise sounds

Core Design Contradiction:

ReliabilityVSObject-generated harmful factors

Solution Approach 1:

The system dynamically adjusts the loop gain based on environmental noise characteristics rather than using a fixed high gain. This adaptability allows the system to achieve effective noise reduction at problematic frequencies while avoiding the instability and unwanted sounds that result from consistently high gain settings.

Inventive Principle:

Principle #15Dynamics

Solution Approach 2:

The patent employs feedback by monitoring environmental noise levels with an external microphone and using this information to adjust the ANR parameters. This feedback mechanism enables the system to respond to changing acoustic conditions and optimize performance while minimizing harmful artifacts.

Inventive Principle:

Principle #23Feedback

3Adaptability or versatility

If feedback-based ANR operates across wide frequency range, then coverage of environmental noise is improved, but device complexity and processing requirements increase

Engineering Contradiction:

Improvefrequency coverage rangeVSAvoidsignal processing complexity

Core Design Contradiction:

Adaptability or versatilityVSDevice complexity

Solution Approach 1:

The system dynamically configures the frequency response characteristics of the ANR filters based on the spectral content of environmental noise. Rather than continuously processing all frequencies at full complexity, the system adapts its filter coefficients to target the specific frequency ranges where noise is present, reducing overall processing complexity while maintaining wide effective coverage.

Inventive Principle:

Principle #15Dynamics

Applied Scientific Principles

This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.

Function Achieved in This Case

The solution effectively extends battery life, improves noise reduction across a broader frequency range, and minimizes unwanted noise generation, providing a more efficient and pleasant audio experience.

Implementation Method 1

monitoring a signal output by the external microphone to measure a sound pressure level of the environmental noise sounds detected by the external microphone

Methodology Applied

Scientific EffectSound pressure level detection: Sound

Implementation Method 2

ANR headphones in which unwanted environmental noise sounds are countered with the active generation of anti-noise sounds

Methodology Applied

Scientific EffectActive noise reduction: Acoustic Absorption

Data Source

PatentUS8208650B2Feedback-based ANR adjustment responsive to environmental noise levels

Publication Date: 2012.06.26 BOSE CORP

AI summary

An ANR circuit, possibly of a personal ANR device, monitors a sound level of environmental sounds detected by a microphone external to an earpiece in which the ANR circuit is providing feedback-based ANR, and increases or decreases the degree of feedback-based ANR provided in response to the external microphone detecting a higher or lower sound level, respectively. Increasing and decreasing the degree of feedback-based ANR provided may be carried out by changing a variable loop gain of the ANR circuit and/or a range of frequencies of environmental sounds attenuated by the feedback-based ANR.